I need an iPhone app but I owe money and I don’t have it

"If none of your payment methods can be charged, your account shows a negative balance. You can't buy more items or update your apps until you update your payment method." From: How apps, content, and subscriptions from Apple are billed - How apps, content, and subscriptions from Apple are billed - Apple Support

if you have iOS 17.3.1, then open AppStore and then click on your name icon at top right corner. Then select “Purchased”

Ihatecheaters wrote:

I need a couple of apps but I owe apple 21 dollars

Apple will probably insist you settle any debts before incurring new ones.

same along those lines. can i update my phone if i owe money?

I need a couple of apps but I owe apple 21 dollars